This invention relates to liquid metal cooled nuclear reactor constructions.
One known example of liquid metal cooled nuclear reactor construction comprises a primary vessel suspended from the roof of a containment vault, the primary vessel containing a pool of coolant in which the reactor core is submerged. The primary vessel is sealed at its rim to the roof of the vault and contains an inert cover gas for the pool of coolant. A leak jacket or catchpot enveloping the primary vessel is also suspended from the roof and serves to catch coolant in the event of a leak from the primary vessel.
When the reactor is in operation the temperature of the concrete at the underside of the roof is approximately 40.degree. C. whilst the temperature of the coolant in contact with the wall of the primary vessel is approximately 400.degree. C. so there is a large temperature differential over the upper strakes of the primary vessel. This temperature differential creates a stress problem in the primary vessel and at its sealed connection with the roof of the vault.
In U.S. Pat. No. 4,022,656 means for alleviating this stress problem is disclosed. The means comprises a cooling jacket and thermal insulation cladding an upper region of the primary vessel and arranged progressively to reduce the temperature of the vessel wall towards the roof of the vault.
An object of the present invention is to modify the reactor construction in such a manner that complex stresses in the wall of the primary vessel are largely avoided.